| You might have heard of an old trick in the world | | | | your accessories. These are called underdrive |
| of automotive performance that uses special | | | | pulleys. The most obvious difference between an |
| pulleys to somehow pick up more horsepower | | | | underdrive pulley and a standard pulley is that it |
| from an otherwise stock motor. This might seem | | | | has a smaller diameter. This makes it so that the |
| a little too good to be true, but actually it is a | | | | pulley does not turn as fast as the stock pulley, |
| proven technique that you could apply to your | | | | meaning that less energy is used in the motion. |
| engine in order to increase performance. | | | | More importantly, these pulleys are also much |
| How does it work? Well, keep in mind that your | | | | lighter than a stock pulley, and the reduced mass |
| engine is providing power to more than just the | | | | makes them far easier to rotate. It is this last |
| wheels of your car. For example, the alternator, | | | | feature which gives you the biggest performance |
| the air conditioning compressor, and the power | | | | gains. Usually you can access about 3 to 5 free |
| steering pump are all connected to the engine | | | | horsepower with these devices. |
| through a belt and pulley system. Each of those | | | | I know what you are thinking if the pulleys are |
| accessories has a small pulley that gets rotated | | | | not spinning as fast as they used to, doesnt this |
| by your serpentine belt that big belt located at | | | | mean that my accessories are not going to get |
| the front of the engine. These pulleys take a | | | | the power that they need to work properly? Yes |
| small amount of horsepower from the engine in | | | | and no. It is usually safe to underdrive your |
| order to keep turning and working while you are | | | | accessories by about 20 percent. If you go below |
| driving. This is known as parasitic drag. | | | | this point, you might start to notice issues like an |
| Now, normally this is not an issue. After all, the | | | | alternator which does not generate enough |
| amount of energy it takes to turn two or three | | | | electricity to keep the engine running, or a power |
| small pulleys is in the 5 to 7 horsepower range. No | | | | steering pump that you have to fight against in |
| big deal, right? Well, when you are trying to | | | | order to turn the wheels. These issues, when |
| squeeze every last drop of performance out of | | | | they appear, usually occur only at idle. This is why |
| your engine, you should grab whatever you can. | | | | the 20 percent limit is recommended on a street |
| If this horsepower is there for the taking, why | | | | car. If you are running primarily on the track, |
| not scoop it up? | | | | where you will see wide open throttle most of |
| The way to eliminate a substantial portion of this | | | | the time, then you can take the chance of |
| parasitic drag is to install special pulleys that take | | | | running a more aggressive set of pulleys that will |
| less energy to turn yet are still capable of running | | | | reduce parasitic drag by a greater amount. |